U.S. television networks have aired video of a Marine in Iraq shooting dead at close range an apparently unarmed and severely wounded insurgent inside a Fallujah mosque.

U.S. military officials are investigating the incident videotaped by Kevin Sites, a journalist traveling with the Marine unit that entered the mosque Saturday to find 10 dead and five wounded insurgents lying on the floor.

The fighters had battled another Marine unit on Friday. The journalist says the wounded were left in the mosque for other troops to take for treatment, but that did not happen.

A Marine is heard shouting that a wounded insurgent was faking death, then is seen shooting the man.

The Marine, who was wounded Friday but returned to duty, has not been identified.